This invention relates to a machine tool, and more particularly to a complex machine tool having composite machining functions and arranged so as to enable a plurality of machining processes to be made on a workpiece once loaded or mounted thereon.
Heretofore, most of the combination of machining processes includes milling, boring and drilling etc. i.e. cutting work by rotation of tool, and there is few combining a turning process. Furthermore, the two machining systems have substantially lost their inherent applicabilities to general purposes for use because of troublesome tool replacing and positioning operations, and have been semi-exclusively used. Consequently, the rate of operation of them could not be improved on the production line for manufacturing a small amount of products of various kinds.
In view of the above-mentioned circumstances, numerical controls (NC) of machine tools have been rapidly developed since 1960, and automatic tool changers (ATC) have been used jointly with them, and therefore complex machine tools having high applicabilities to general uses have appeared in the market. In particular, the "Machining Center" has been employed widely as a representative one at the recent time.
However, these machining systems comprise milling machines or boring machines as base machines and have their principal functions to effect cutting of workpieces by rotating their tools, and therefore turning work has been required to be made by means of a separate or independent machine.
For this reason, if the turning work is made by means of the machines, it is required to effect profile cutting by means of a small-diameter end mill, as a result a number of problems are encountered such as a remarkable increase in the number of cutting processes, decreased economy of operation and also incapability of obtaining a predetermined initial surface roughness of a workpiece to be machined etc. On the other hand, the turning machine has been advanced in a single-function automation, however delayed in having complex function. The prior art for it includes U.S. Pat. Nos. 3,523,469, 3,703,027, 3,212,364 and 3,851,364; however, any of these is arranged to rotate the table at a fixed position, stated more specifically, they are only conventional turning machines each having a table rotating and indexing arrangement mounted thereon or having a ram means provided with a rotary tool mounting head. Therefore, in turning work, the workpiece can be turned or cut only by the face of the tool in parallel with the cross rail passing through the centre of the table so that the tools to be mounted on the tool arbor can be located only in the above-mentioned plane. Thus, the number of the tools to be mounted thereon is limited thereby increasing the number of times of replacement of tools.
Further regarding the milling, boring and drilling work etc. to be combined, because of the table of stationary type, when machining the face of a workpiece in parallel with the table or the upper surface of the workpiece placed on the table, the parts of the workpiece other than that placed on the circumference thereof require a programme to be made for determining a machining position by calculating coordinates based on the relationship between the table indexing angle and the position of the saddle, and the operation becomes complicated or troublesome. Furthermore, regarding machining of the face of the workpiece at right angles to the table face or the side of the workpiece mounted on the table, only centripetal machining of it can be effected, and therefore faces of the workpiece in parallel with the central axial plane thereof cannot be machined.